Practice devices for various sports are known. For example, U.S. Pat. No. 2,471,610 to Christensen for "Rotatable Practice Ball Bat", May 31, 1949, describes a practice device for a batter which permits free rotation of the bat as the ball is struck, thus informing the batter when the ball is not struck squarely. U.S. Pat. No. 3,351,346 to Strahan for "Golf Swing Training Device", Nov. 7, 1967 proposes a golf practice device involving a shaft attachment of an extension to the golf club handle having a straight and bent portion, the latter having weights attached. The device is intended for use to inculcate a proper swing. U.S. Pat. No. 3,880,423 to Kreag for "Baseball Bat Having Different Striking Surfaces", Apr. 9, 1975, proposesa novel bat, not rotationally symmetrical about an axis as is a conventional bat, for a ball game different from the conventional ball game, and employing targets to be hit by the ball after it is batted by the bat. U.S. Pat. No. 3,955,816 to Bratt for "Warm-up Bat", May 11, 1976, describes a sleeve for attachment to the batting portion of the bat for adding weight to the bat for the batter's warm-up.
U.S. Pat. No. 4,214,751 to Simpson for "Adjustable Bunting Bat With Protective Shield", July 29, 1980, describes an insertable bat handle section for shortening a baseball bat, and a shield for protecting the hand of the batter, when the section is inserted, so that he may practice one-handed bunting with the shortened bat, thereby learning the proper way of holding the bat for a bunt.
My U.S. Pat. No. 4,595,204 for "Device For Practicing Golf Club Swing", June 17, 1986 describes a device for practicing a golf swing. This device is an elongated extension removably attached to the handle of the club to extend normally upwardly under the left arm pit to a level about the level of, and behind the shoulders. This device aids in perfecting a proper golf driving swing.